Rheokinetic of polyurethane crosslinking time‐temperature‐transformation diagram for rotational molding

Abstract

In this work, the rheokinetic of polyurethane crosslinking was studied by different methods: differential scanning calorimetric (DSC), rheometry, and infrared spectrometry. The conversion ratio and the glass transition temperature were followed by time of reaction. The results of the isothermal and nonisothermal test were compared. The evolution of viscosity was measured at different frequencies. The intersection of these curves is considered as gel point. A simplified mechanism has been proposed for crosslinking reactions. Based on this mechanism, a kinetic model describing the evolution of reactive system was developed. This model then was compared with the results of experiments performed by infrared spectrometry. The time-temperature-transformation diagram was established showing the evolution of physical state change of the reactive system. This diagram may be used to evaluate the zone of rotomoldability of the reactive polyurethane.

Construction of improved isothermal TTT cure diagram based on an epoxy–amine thermoset

“…Classic isothermal time–temperature‐transformation (TTT) diagram can describe the changes in physical states during the cure process and it can serve as a powerful tool for understanding the curing process of thermosetting resin in Figure . Three main curves named the gelation, vitrification, and full curing curves divide the TTT diagram into several regions, each region corresponding to a distinct state of the thermosetting system, which include liquid, sol glass, sol/gel‐rubber, gel‐rubber, sol/gel‐glass, gel‐glass, and char . These curves of gelation and vitrification have been determined by many methods.…”

“…2,3 Three main curves named the gelation, vitrification, and full curing curves divide the TTT diagram into several regions, each region corresponding to a distinct state of the thermosetting system, which include liquid, sol glass, sol/gel-rubber, gel-rubber, sol/gel-glass, gel-glass, and char. 3,4 These curves of gelation and vitrification have been determined by many methods. For instance, the gelation of the resin is obtained by thermomechanical analysis and dynamic mechanical analysis, T g and the curing degree of resins is determined by differential scanning calorimetry (DSC).…”

Time‐temperature‐transformation diagram of modified resol phenolic resin and the thermomechanical performance of resol phenolic resin/glass fabric composite

“…T g 0 (−5.3°C) corresponds to T g of MPR at α = 0. In the case of lower temperature, the components do not react and the rate of the cross‐linking reaction can be neglected, indicating that the uncured resins can be stored below T g 0 . During the temperature of T g 0 (−5.3°C) and T g ,gel (122°C), MPR can vitrify before gelation, forming a liquid glass.…”

Modelling surface tension with smoothed particle hydrodynamics in reactive rotational moulding

“…Once the reaction starts, the viscosity increases according to the rheokinetic model [38] used in this study, which gives the relationship between viscosity and the rate of reaction. The parameters of the adhesion models chosen are: g adhe ¼ 9 Pa s, t adhe = 3 s and…”